Continuously-loaded conductor



Dec, 16, 1924. n 1,519,220

E. SCHURER CONTINUOUSLY LOADED CONDUCTOR Filed Aug. 6, 1923 Patented Dec. 16, 1924.

UNITED STATES EUGEN SCI-FUREB, 0F COLOGBTE-"VIULHEIM, GERMANY.

CONTINUOUSLY-LOADED CONDUCTOR.

Application filed August 6, 1923.

To all whom "it may concern:

Be it known that I, EUGEN Sorrfinnn, a citizen of the German Republic, residing at Cologne-Mulheim, Genovevastr. 94, Germany, have invented certain new and useful Improvements in and Relating to Continuously-Loaded Conductors, of which the following is a specification.

This invention relates to an annealing process for continuously loaded conductors for adjusting the self-inductance per unit length of manufactured lengths of such conductors to a definite constant value within the limits determined by the loading ma.- terial that is used.

As is known, continuously loaded conductors are conductors which, for the purpose of artificially increasing their self-inductance, are wound round in close spirals with one or more layers of thin wire of magnetizable material, that is to say, preferably iron or irons alloys. As the thin loading material is subject to a certain amount of hardening and in consequence thereof to a certain reduction in its permeability in consequence of the bending stresses during winding on the copper conductor, it is usual to anneal the continuously loaded conductor after it has been wound with the loading material in order thereby to soften again the material and again impart thereto its maximum permeability.

lVhen such conductors are used for the manufacture of electrically homogeneous telephone and telegraph cables, it is important, as is well known, that the self-inductance per unit length of the lengths of manufacture of which the cable is constituted shall be of constant value. Hitherto it has not been possible to fulfill this condition with sufilcient eXactitude. The differences between the values of self-inductance per unit length of the individual manufactured lengths and the normal values are due on the one hand to the fact that the wire that is wound round is not quite uniform as regards its dimensions whereby differences are produced in the weight of the iron per unit of length and consequently also in the selfinductance, and on the other hand to the fact that the re-instating of the permeability that is aimed at by the annealing of the Serial No. 656,135.

conductor provided with the winding is de pendent on the hardening in the cold of the w0undon material that arises by the wind ing on the copper conductors and according to the degree of this hardening, gives different values of permeability.

Hitherto it has been endeavoured to remove as much as possible these two causes of inequalities, separately by a more exact and more uniform manufacture. These endeavours however were not sucessfu] because insurmountable obstacles were in the way in the production of equal weights of iron due to the differences in the dimensions of the material to be wound on, which cannot be avoided in mass production.

The solution provided by the present invention consists in that the inequalities pro duced by the said two causes are mutually compensated in their total effect by producing such differences of permeability by the annealing of the wound continuously loaded conductor of each manufactured length that they compensate the differences in the weight of iron by their action on the value of the self-inductance.

The production of these values of permeability required for the compensation is rendered possible according to the invention by following up by measurement the varia tion of the self-inductance during the annealing and by adjusting the latter according to the results of the measurements.

It has been found that during the annealing with gradually increasing temperature, the self-inductance of the continuously loaded conductors, in consequence of the changes in the permeability of the loading material which thereby arises, gradually increases from the value corresponding to the non-annealed condition of the conductors up to the maximum valve that is obtainable by the annealing. It has also been found that it can be ascertained that a ratio exists between the permeability of the conductor in its hot condition and the permeability it has assumed after the cooling. It is thus possible, when the self-inductance of the continuously loaded conductors is followed up by measurement during the annealing with increasing temperature, to interrupt the annealing at the moment when the desired value of the self-inductance is tained. In this way the inequalities in the weight ofthe loading material that is wound on and in the permeability coinpensate each other in their total effect without it being necessary to note the individual differences.

In order to be able to follow up the selfinductance of the continuously loaded conductors by measurement, according to the invention the annealing is not effected according to the known pot-annealing process but by sending an electric current through the continuously loaded conductors. For this purpose the continuously loaded conductor a is wound on a drum 1) of fire-resisting material on which it can be heated to any desired temperature by regulating the strength of the current supplied by a source of current 0 by means of a variable resistance d. At the same time, for instance when the conductor is helically wound in a groove provided on the drum, it is possible to measure its self-inductance on the drum. The simultaneous annealing and measuring is rendered possible by the self-inductance being determined either by measuring the output of the annealing current and its strength and voltage, or by alternately connecting the conductor by means of an automatic switching device 6 (which is connected to a clockwork mechanism) at regular intervals to the source 0 of the annealing current and to a measuring device f, for instance a VVheatstone alternating current bridge, the said intervals being so short that during the measurement the conductor is maintained at the annealing temperature.

The switching device 6 is operated by a clockwork mechanism 1 through the intermediary of an electromagnet 2 inserted in an electric circuit of the clockwork mechanism and energized by means of a current derived from a source 3. The switching device is under the control of a spring 4 attached to a stationary part 5 and is provided with an iron armature 6 upon which acts the electromagnet 2.

The regulation of the annealing tempera ture by a corresponding regulation of the strength of annealing current permits of attaining in addition to the described processes also an exact regulation of the rate of cooling, since the current can be gradually reduced to Zero at any desired rate. This is a further advantage of the annealing by heat obtained from an electric cur rent, since the rate of cooling is of deciding influence on some iron alloys as regards final value of the self-inductance and permeability of the loading material. In order to prevent too strong an oxidation of the wound-on wire in the case of cooling of long duration, according to the invention the drum supporting the continuously loaded conductor is enclosed in a receptacle g which, for the purpose of keeping away the oxygen that is in the air, is either evacuated or traversed by a neutral gas in a manner that is known per se, cocks h being provided for the admission thereof.

What I claim is 1. A process for producing equal values of self-inductance per unit of length of each length of manufacture of a continuous ly loaded conductor, consisting in annealing the wound continuously loaded conductor to such extent that such values of permeability are obtained in each length of manufacture that in spite of the difierences in the weight of the iron all the lengths of manufacture obtain the same value of self-inductance per unit of length.

2. A process for producing equal values of self-inductance per unit of length of each length of manufacture of a continuously loaded conductor, consisting in annealing the wound continuously loaded conductor to such an extent that such values of permeability are obtained in each length of manufacture that in spite of the differences in the weight of the iron all .the lengths of manufacture obtain the same value of self-inductance per unit of length,

the change in the self-inductance being followed up by measurements during the annealing for the purpose set forth.

3. A process as claimed in claim 1, in which the annealing is effected by passing an electric current through the wound continuously loaded conductor, and is regulated by adjusting the strength and duration of the said current.

4. A process for producing equal values of self-inductance per unit of length of each length of manufacture of a continuously loaded conductor, consisting in mounting the length of manufacture of a conductor spirally in a groove provided on the periphery of a drum of fire-resisting material, and an annealing the wound con tinuously loaded conductor to such an extent that such values of permeability are obtained that in spite of the differences in the weight of the iron all the lengths of manufacture obtain the same value of selfinductance per unit of length.

5. A process as claimed in claim 2, in which. for the pur ose of facilitating the simultaneous annealiiw and measuring. the conductor is connected alternatelv and at regular very short intervals onto the source of annealing current and to a device for measuring the self-inductance, by means of a switching device, connected to a clockwork mechanism. 7 V

6. A process for producing equal values of self-inductance per unit of length of each length of manufacture of a continuously loaded conductor, consisting in mounting the length of manufacture of a conductor spirally in a groove provided on the periphery of a drum of fire-resisting material enclosed in a receptacle from which oxygen is excluded. and in annealing the Wound continuously loaded conductor to such an extent that such values of permeability are EUGEN SCHURER. 

